Apparatus for forming thermoplastic sheet material



Dec. 10, 1963 R. L. BUTZKO APPARATUS FOR FORMING THERMOPLASTIC SHEET MATERIAL Filed Aug. 24, 1961 5 Sheets-Sheet l ATT'RNEY.

Dec. 10, 1963 R. 1 BuTzKo 3,113,345

APPARATUS FOR FORMING THERMOPLASTIC SHEET MATERIAL Filed Aug. 24. 1961 3 Sheets-Sheet 2 @la @El @gaf 55 [57 ,4N f4J if 57 TTQRNEY Dec. l0, 1963 R. L. BuTzKo 3,113,345

APPARATUS FOR FORMING THERMOPLASTIC SHEET MATERIAL. Filed Aug. 24, 1961 3 Sheets-Sheet 3 9e 9; t es 48,/ 3, I9 @/H 90 n @A n. y n 70 14 Z2 92 1 a L 53 I4 l M f l; m

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93 94' 9 9" INVENTOR.

.5 92 90 92 HEBERT L. BUTZKU AT TURNER' United States Patent O 3,113,345 APPARATUS FR THElT/{OPLAS'I'EC SHEET MATERIAL Robert L. Eutzlro, 94 Nash Lane, Bridgeport 5, Conn. Filed Augs 24, i961, Ser. No. 133,638 Claires. (@Cl., 1819) The present invention relates to apparatus for forming thermoplastic sheet material, and has for `an object to provide apparatus of this character of compact, simpie and inexpensive construction adapted for convenisnt and economical use in research laboratories in the experimental production of .samples of formed products from thermoplastic film or sheet, in the relatively small scaie commercial production of such products, and in other forming operations where large expensive auto matic forming apparatus is not justified.

Another object is to provide a formirny apparatus of combination pressure and vacuum type, by means of which the forming operation may be carried out either by use of pressure or vacuum or by a combination of pressure and vacuum. A further object is to provide improved means for applying mechanical pressure to the mold parts by which a maximum clamping and sealing action may be obtained with a minimum operating effort. Another object is to provide `a forming apparatus which readily adapts itself to the provision of either manual or automatic operating means. A further object is to provide improved means for clamping the thermoplastic sheet and for severing the formed article from the sheet following the forming operation.

Other objects and advantages will become apparent from a consideration of the following detailed description taken in connection with the accompanying drawings wherein a satisfactory embodiment of the invention `is shown. However, it will be understood that the invention is not limited to the details disclosed but includes all such variations and modifications as fall within the spirit of the invention and the scope of the appended claims.

in the drawings:

FIG. l is a :side elevation of the apparatus according to the invention, shown in open position;

FIG. 2 is a front elevation;

FIG. 3 is a side elevation partially broken away showing the apparatus in the operative position during the forming of the thermoplastic sheet;

FIG. 4 is a side elevation showing the apparatus in its final operating position to sever the formed article from the nlm or sheet;

FIG. 5 is a sectional view on an enlarged scale of a heater platen and cavity mold as employed in the apparatus;

FlG. 6 is a detailed sectional view on a further enlarged scale showing the rst step in the forming operation where the thermoplastic sheet is clamped between the heater platen and the cavity mold;

FIG. 7 is a similar View showing the article formed in the cavity mold;

FIG. 8 is a similar view showing the formed article severed from the lm or sheet;

FIG. 9 is a side elevation of a modified form of the apparatus adapted for automatic operation;

PEG. l0 is a side elevation of another modified form of the apparatus adapted for manual operation and mannal control of the article severing means;

FIG. ll is a detailed view on an enlarged scale of the cam means employed in the embodiment shown in FIG. l() in one operative position during the forming operation; and

FIG. l2 is a similar view showing the cam means in 2 another operative position during the article severing operation.

Referring to the drawings, the rapparatus for forming thermoplastic sheet material according to the exemplary `embodiment of the invention illustrated in FlGS. l-8 comprises a kbase 1t) provided along the side edges of its upper side with a pair :horizontal spaced parallel angle iron strips 11-11 which project rearwardly and pivotally support upon a pivot rod 12 a pair of forwardly extending arms 13, between the forward ends of which there is supported a heater platen 14. A pair of downwardly and rearwardly inclined lever arms 1S are secured as by welding to the rearward ends of fthe arms 13 and are respectively `connected by springs 16 to brackets 17 secured at each side of the base lll, and which function as counterbalance means to normally move the heater platen 14 to its open position as seen in FIGS. 1 and 2, which open position is limited by stop means hereinafter more `fully referred to.

At each side of the heater platten and supported in the base 10 there is provided a pair of vertically threaded posts 18-18 -mounted at their lower ends by means of nuts 19 upon horizontal angle iron cross bars 2li--2`0 secured wiihin the base, `clearance holes 2li being puovi'ded in the angle iron strips 11 for receiving the posts.

The cavity mold 22 is mounted upon a plate 23 which in turn is supported `for vertical `adjustment upon the pairs Iof posts 18, being provided for this purpose at each end with holes 24 engaged by the posts, nuts 25 being secured upon the posts above and below the plate to secure the plate in -its position of Ventical adjustment.

A roll 26 or" the thermoplastic sheet material 27 is mounted by means of a spindle 2S in notches 29 of brackets 30 provided at the rear of the base 1li so that the sheet material may be conveniently drawn from the roll over the cavity mold 22 as clearly shown in FIG. l.

A pair of bearing blocks 3l. having vertical passages 32 are engaged upon the upper ends of the threaded posts 18, and secured in their position of vertical adjustment by nuts 33 and 34 secured upon the posts above and -below the blocks. A pair of horizontal bracing strips 35 having holes 36 at their ends for receiving the posts are secured between the upper sides of the bearing blocks and the nuts 33 and extend transversely between lthe blocks. A vertically disposed plate 37 extends transversely between and is secured to the rearward sides of the blocks by screws 33 for the purpose of rigidly conmeeting the blocks and providing a support for certain parts of the apparatus, presently more fully referred to.

A transverse shaft 39 is rotatably engaged in bearing holes itl-40 in the pair of bearing blocks 31 and is positioned `against axial movement by collars 41-41 cured upon the ends of the shaft. Upon the shaft adjacent the inner sides of the blocks there are secured the hub ends ot a pair of forked crang levers 42, the outer ends of which are connected by pivot pins 43 to links 44 which -in turn are vconnected by pivot pins 45 to brackets 46 secured to the upper side of the heater platen 14, the position of the brackets upon the heater platen being such that in the closed position, as seen in FIG. 4, with the toggle leverage provided by the crank levers and links vertically disposed, the axes of the pivot pins 4S, -the pivot pins 43, and the shaft 39 are: in vertical line.

A pair of Spanner plates 47 extend between the forked crank levers 42 and are rigidly secured to their forward and rearward sides as by welding so that the two forked crank levers form a rigid unit. A forwardly extending actuating handle 4o is engaged at its inner end in holes 49 in the Spanner plates 47, and is rigidly secured thereto as by welding, this handle being of sufficient length to provide high leverage for the convenient manual operation of the toggle connection between the shaft 39 and the heater platen. The open position of the platen is limited as seen in FIG. l by engagement of the handle 43 with the forward bracing strip 35 under the action of the springs 16, the strength of these springs being such in relation to the Weight of the heater platen that the latter is slightly overbalanced by the action of the springs to normally retain the parts in the open position while at the same time offering only slight resistance to the manual actuation of the toggle connection to move the heater platen to closed position.

An arm S preferably formed of channel iron is rigidly secured as by welding to the lower edges of the Spanner plates 47 between the pair of forked crank levers i2 and projects rearwardly therefrom for the purpose of cooperiating with stop means to limit the closed positions orr the heater platen as will presently more fully appear.

As seen in FIG. the heater platen ld comprises a body member 5l provided at its under side with a heater plate 51a, the planar face surface of which is in communication through substantially equally distributed spaced passages 52 of very small diameter with a manifold channel 53 in the body member having a exible pipe connection 54 with a source of vacuum or sub-atmospheric air as well as to la source of pressure `or super-atmospheric air, the selective control of `vacuum or pressure being provided by suitable timer actuated valve means (not shown) in wellknown manner. The heater platen is heated in wellknown manner by Calrods 55 suitably distributed in the body member 5l and to which electrical current is supplied through a flexible cable connection 56.

The cavity mold 2.2 is provided with a cavity 5'7 of suitable shape to produce the desired article, and is in communication through suitably disposed passages 58 with a manifold channel 59 in the supporting plate 2.3 in cornmunication through a pipe connection o@ with a source of vacuum or sub-atmospheric air, as well as a source of pressure or super-atmospheric air, selectively controlled in well-known manner by timer actuated valve means.

At the upper side of the cavity mold and corresponding in shape to the outer edge of the article to be formed there is provided a cutter blade member 6l, shown in the illustrated example as a circular band seated in an annular shouldered recess 62 and secured by a retaining ring 63. This blade is adapted, as will presently more fully appear, to sever the formed article from the thermoplastic sheet, and for this purpose the projection of its severing edge above the upper side of the rim surrounding the cavity 57 corresponds substantially to the thickness of the thermoplastic sheet.

In the operation of the apparatus the thermoplastic sheet material is first drawn forwardly over the cavity mold where it rests upon the upper edge of the blade member 61. Thereupon the heater platen is moved to its lirst closed position as seen in FIGS. 3 and 6 to clamp the material between the flat surface of the heater platen and the upper edge of the blade member and to cause the blade member to partially penetrate or indent the thermoplastic sheet. Simultaneously with this action the sheet is maintained in flat contact with the heater plate either by applying vacuum yat the upper side or pressure at the lower side or a combination of vacuum and pressure at the upper and lower sides. This first closed position of the heater platen is determined by the engagement of the arm 50 with the projected plunger 64 of an air cylinder 65 mounted upon the transverse plate 37, air under pressure to retract and project the plunger being supplied through pipe connections 66 and 57 which extend to suitable timer controlled valve means (not shown).

The operating cycle of the apparatus is started as the handle moves to its first closed position by means of an arm 68 rigidly secured upon one end of the shaft 39 and provided with an adjustable control screw o@ which actuates the contact button 7 ti of a microswitch 7l connected by a cable 72 with suitable valve actuating timer means.

As soon as the thermoplastic sheet becomes heated to the desired molding temperature, the timer which is set to predetermine the heating time actuates the valve means to reverse the pressures upon the thermoplastic sheet to cause it to be moved through deformation into conforming relation with the cavity 57 of the cavity mold. Such movement may be produced either by pressure at the upper side or vacuum at the lower side or a combination of pressure and vacuum. During this forming operation it will be seen that the thermoplastic Sheet is securely clamped and sealed at the point marking the outer periphery of the formed article by the partial penetration of the blade member as seen in FIG. 7. When the article is formed and set through contact with the relatively cool cavity mold, it is severed from the thermoplastic sheet, and to this end the handle lil is moved from the position as seen in FIG. 3 to the position as seen in FlG. 4, bringing the toggle leverage to its straight position and causing the blade member to fully penetrate the thermoplastic sheet and seat against the heater platen. This action is brought about by actuation of the air cylinder 65 to retract the plunger 64 to the position as seen in FIG. 4, allowing an Iadjustable stop member 73 carried by the arm 5@ to move into an engagement with a stop bar 7d secured as by welding to the lower edge of the transverse plate 37. The stop member 73 is preferably in the form of a headed screw threaded into the arm Sti and provided with a lock nut 75 to fix its position of adjustment. The arrangement of the toggle leverage is such that tinal lowering movement of the heater platen to sever the formed article is of a very small order compared to the angular movement of the handle 48. Upon raising the heater platen at the completion of the operating cycle ithe formed `article may be subjected to air pressure at the under side to assist in its removal from the mold.

As seen in FIGS. l and 2 the base lil is provided at one side with a suitable control cabinet 76 provided with a temperature control unit 7'7, on-and-ott switches 7S, a timer :control unit 79, and suitable pilot lights S6 and $1. Suitable vacuum and pressure units are housed within the base and are accessible through a removable screen guard S2. Further detail illustration and description of the control means and the connection of the cables, pipes and valves thereto is not `deemed necessary as the practice in this respect is well known.

In FIG. 9 there is `shown a modification in which the toggle leverage comprising the shaft 39, the crank lever 42 and the link 4d is adapted to be power operated. To this end a lever 83 is secured upon the shaft 39 and is pivotally connected to the piston rod S4 of an -air cylinder 85 pivotally mounted upon a bracket S6 supported upon a right angle shelf extension 87 of the transverse plate 37. The cylinder is provided with iiexible pipe connections S8 and 99 extending to a source of high pressure air provided with timer controlled valve means for projecting and retracting the piston rod to impart closing and opening movement to the platen. The measure ratio between the air cylinder $5 and the air cylinder 65 is such that the holding pressure of the plunger 6d in its projected position is greater in the closing pressure ot the cylinder 5, so that the platen is limited in its initial closing movement to the position `as shown in FIGS. 6 and 7 where the cutter blade 6l partially penetrates the thermoplastic sheet 27, full closing movement to sever the thermoplastic sheet being permitted upon the timer controlled retraction of the plunger 64.

lIn FIG. 10 there is shown a further modification adapted for full manual control of the platen closing operation. The manually oper-able handle 43a is of tubular form and rotatably supports a shaft Qt) having a rotatable hand grip 9i secured upon its outer end and a cam 92 secured upon its inner end, the cam being provided with a high part 93 and a low part 94. A stop pin 9S secured to the shaft 88 moves in a limit slot 96 provided in the tubular handle 48a to limit the rotation of the hand grip 9i. ln swinging the handle downwardly to bring the platen into its initial closed position the cam is in position so that its high part 93 contacts the stop bar 74, thus limiting the movement of the platen to the position as seen in FIGS. 6 and 7. Upon completion of the forming operation the hand grip 91 is rotated to bring the low part 94 of the cam into engagement with the stop bar 74 as seen in FIG. 2, whereupon the handle 48a is permitted to move downwardly to its full closing position to bring the platen into the position `as seen in FiG. 8 where the blade member 61 fully penetrates the thermoplastic sheet and severs the formed article therefrom.

What is claimed is:

1. Apparatus for forming thermoplastic sheet material, comprising a forming mold, a heater platen, cutter blade means carried by said mold having a continuous outline shape deiining the peripheral outline of the article to be formed therein `and projecting therefrom a distance at least equal to the thickness of the thermoplastic sheet to be formed, means for bringing said mold and platen into and out of closed relation with the thermoplastic sheet -between them spanning said cutter blade means `and having a margin entirely surrounding said cutter blade means, means for limiting the closed relation to a point at which said thermoplastic sheet is clamped between said platen and said blade means without full penetration `of said sheet by said blade means, means for applying differential air pressures to said sheet Ito successively hold it in contact with said heater `platen and Ito form it in a heated plastic state into conformity with said mold, and means for rendering said limit means inoperative .to permit full closing movement and full penetration of said sheet by said blade means to sever a formed article from said sheet.

2. The invention as defined in claim l, further characterized in that said limit means comprises ra fluid pressure unit having -a plunger `adapted in ya projected position to limit said closed relation to said point at which said thermoplastic sheet is clamped between said platen and said blade means, `and in a retracted position to permit said full closing movement.

3. The invention as defined in claim 1, further characterized by manually movable limit means adapted in one position to limit said closed relation to said point at which said thermoplastic sheet is clamped between said platen and said blade means, and in `another position to permit said full closing movement.

4. Apparatus for forming thermoplastic sheet material, comprising a forming mold, ya heater platen, cutter blade means carried by said mold having a continuous outline shape dening the peripheral outline of the article to be formed therein and projecting therefrom a distance at least equal `to the thickness of the thermoplastic sheet to be formed, means `for bringing said mold and platen into and `out of closed relation with the thermoplastic sheet between them spanning said cutter blade means and llaving a margin entirely surrounding said cutter blade means, means for limiting the closed relation to -a point at which said thermoplastic sheet is clamped between said platen and said blade means with partial penetration of said sheet by said blade means, means for applying differential air pressures to said sheet to successively hold it in contact with said heater platen and to form it in a heated plastic state into conformity with said mold, and means for rendering said limit means inoperative to permit full closing movement and full penetration of said sheet by said blade means to severa formed article from said sheet.

5. Apparatus for forming thermoplastic sheet material, comprising a base, a forming mold carried by said base, a heater platen, support means for said heater platen pivotally mounted on said base for bringing said platen into and out of closed relation with said mold, cutter blade means carried yby said mold having a continuous outline shape defining the peripheral outline of the article to be formed therein and projecting therefrom a distance at least equal to `the thickness of the thermoplastic sheet to be formed, a transverse shaft mounted on said base in line with said platen and mold, toggle leverage means connected between said shaft and said platen, means for imparting movement to said ytoggle leverage means to move said platen into and out `of closed relation with said mold with the thermoplastic sheet between them spanning said cutter blade means and having a margin entirely surrounding said cutter blade means, means for limiting the closed relation to a point at which said thermoplastic sheet is clamped between said platen and said blade means Without full penetration of said sheet by said blade means, means for applying dilerential :air pressures to said sheet to successively hold it in contact with said heater platen and to form it in a heated plastic state into conformity with said mold, and means for rendering said limit means inoperative -to permit full closing movement and full penetration of said sheet by said blade means to sever a formed article from said sheet.

References Cited in the tile of this patent UNITED STATES PATENTS 1,904,268 Bronson Apr. 18, 1933 2,691,797 Bertleif et al. Oct. 19, 1954 2,814,074 Butzko Nov. 26, 1957 2,836,852 Butzko lune 3, 1958 

1. APPARATUS FOR FORMING THERMOPLASTIC SHEET MATERIAL COMPRISING A FORMING MOLD, A HEATER PLATEN, CUTTER BLADE MEANS CARRIED BY SAID MOLD HAVING A CONTINUOUS OUTLINE SHAPE DEFINING THE PERIPHERAL OUTLINE OF THE ARTICLE TO BE FORMED THEREIN AND PROJECTING THEREFROM A DISTANCE AT 